CN1638005A - Magnetron - Google Patents

Abstract

A magnetron capable of suppressing the capacitance portion Cr of a cavity resonator to be small, and achieving both improvement in operation stability and high efficiency. In the anode frame (51) of the magnetron, a plurality of plate-shaped blades (54) radially equipped on the inner peripheral surface of the roughly cylindrical anode cylinder (53) pass through the anode cylinder (53) The front end portion on the central axis side of the front end is made into a stepped shape Df in which the plate thickness from the front end to the predetermined length L is thinned, so that the area of the adjacent plate-shaped blades (54) facing each other can be suppressed from increasing, and at the same time, the front end of the blade can be ensured. distance between sections.

Description

Magnetron

technical field

The present invention relates to magnetrons for microwave application equipment such as microwave ovens.

Background technique

As shown in Figure 5, a magnetron installed in a microwave oven or the like as a microwave oscillating device is generally composed of a vacuum tube part 1 at the center, a plurality of cooling fins 2 for heat dissipation on the outer periphery of the vacuum tube part 1, and a vacuum tube part. A pair of ring magnets 3 coaxially arranged in the part 1, frame-shaped yokes 4 and 5 magnetically connecting the ring magnets 3, and a filter circuit part 7 are constituted. The vacuum tube unit 1 is composed of an anode frame 11 and a cathode frame 21 mounted on the central axis of the anode frame 11 .

The anode framework 11 is shown in Figure 6 and Figure 7, and its structure comprises: a substantially cylindrical anode cylinder 12, fixedly mounted on the anode cylinder 12 radially from the inner peripheral surface of the anode cylinder 12 to its central axis. An even number (N pieces) of plate-shaped blades 13 that maintain a predetermined distance from the filament 22 of the cathode frame 21 is arranged at the end of the tube-axis direction of the plate-shaped blades 13 and every other plate-shaped blades 13 are connected to each other for electrical short circuit Two groups of clamping rings 15, 16 of the same size and the antenna 17 connected on the plate-shaped blade for microwave output.

The cathode frame 21, as shown in FIG. 5 , has a structure comprising: a coiled filament 22 disposed at its center, end caps 23 and 24 joined to both ends of the filament 22 and connected to the filament 22 through these end caps 23 and 24 The cathode supporting lead 25 (for example, refer to Patent Document 1).

In the magnetron of the above-mentioned structure, by heating the filament 22, a prescribed DC high voltage is applied between the filament 22 and the plate-shaped blade 13, and the electrons emitted from the filament 22 to the plate-shaped blade 13 are transferred between the plate-shaped blade 13 and the filament 22. The action space 31 between them is acted by the orthogonal electromagnetic field, orbiting while rotating around the filament 22, towards the plate-shaped blade 13 of the anode frame 11, passing through the cavity formed by dividing the even number of plate-shaped blades 13 The weak microwaves generated in the resonator 33 interact to generate larger microwaves in the cavity resonator 33 , and the generated microwaves are output from the antenna 17 .

The frequency of the microwave generated in the hollow resonator 33 is formed by the inductance part L formed by the inner peripheral wall surface of the anode cylinder 12 forming the hollow resonator 33 and the facing plate-shaped blades 13, and by the plate-shaped blades 13 and by each other. The capacitive part Cr of the hollow resonator 33 composed of the anode cylinder 12 and the capacitive part C synthesized by each clamping ring 15, 16 and the capacitive part Cs composed of the opposite part of the plate blade 13 are determined. The general resonance frequency fr is as follows Formula (1) expresses.

fr=1/{2π(LC) ^1/2 } ... (1)

This frequency becomes the strongest stable oscillation in the magnetron oscillation form, the frequency of the so-called π-mode oscillation in which the phase is reversed between adjacent cavity resonators, and the plate-shaped blades 13 are connected to each other and electrically short-circuited. The main function of the rings 15, 16 is to maintain the stability of this π-mode oscillation.

However, in the magnetron, if N hollow resonators divided by N plate-shaped blades 13 are electrically connected to each other, and then two groups of clamping rings 15, 16 are used to make the plate-shaped blades 13 short circuit alternately, it will There are N/2 oscillations of different frequencies.

For example, if the number N of plate-shaped blades 13 is 10, the number of cavity resonators 33 divided by the plate-shaped blades 13 is 10, and there are 5 oscillation modes according to N/2 as the basic mode. N/2 mode, N/2-1 mode, N/2-2 mode, N/2-3 mode and N/2-4 mode of π mode.

In π mode, operating conditions such as frequency and anode voltage allow for the strongest and stable oscillation. However, if the oscillation frequency of the N/2-1 mode adjacent to the π mode is close to the oscillation frequency of the π mode, even if the operating conditions change slightly, it will shift from the π mode to the N/2-1 mode and oscillate. Unstable phenomena such as mode jumps.

Here, in order to separate the oscillation frequency of the N/2-1 mode from the oscillation frequency of the π mode, it is proposed that each of the capacitive parts Cr of the hollow resonator 33 composed of the plate blades 13 and the anode cylinder 12 The ratio of the clamping ring 15, 16 and the capacitive part Cs of the clamping ring portion formed by the opposite part of the plate blade 13 is set to increase, or the clamping ring 15, 16 does not form a completely symmetrical structure, and cuts off its part of the program. (For example, refer to pages 163 to 165 of Non-Patent Document 1).

On the other hand, it is particularly desired to meet the demand for energy saving in the world in recent years and to increase the efficiency of the magnetron.

In order to increase the efficiency of the magnetron, it is necessary to increase the magnetic field, increase the number of divisions of the anode, and miniaturize the diameter of the anode and cathode, all of which will narrow the distance between the plate blades 13 (refer to 172 to 172 of the above-mentioned non-patented document 1). 177).

Here, even if the intervals between the plate-shaped blades 13 are narrowed, in order to ensure a certain distance between the adjacent plate-shaped blades 13, as shown in FIG. A technology in which a tapered surface 13a is provided on one surface (for example, refer to Patent Document 2).

[Patent Document 1] Japanese Unexamined Patent Publication No. 11-233036

[Patent Document 2] JP-A No. 60-127638

[Non-licensed document 1] "Microwave Vacuum Tube" published by the Association of Wireless Professionals Education in December 1971

However, most of the capacitive portion Cr of the hollow resonator 33 formed between adjacent plate-shaped blades 13 and the anode cylinder 12 is determined by the capacitive portion Cg on the front ends of the plate-shaped blades 13 that are closest to each other, as As shown in FIG. 8( a ), assuming that the facing area of the front ends of the plate-shaped blades 13 closest to each other is S, and the distance between the facing surfaces is d, it is expressed by the following formula (2).

Cr≈Cg＝ε×S/d                (2)

On the other hand, in the structure in which the tapered surfaces 13a are provided on both surfaces of the front end of each plate-shaped vane 13, such a large separation distance cannot be ensured in reality, and as a result, the capacitance Cr of the hollow resonator 33 becomes large.

Fig. 8(b) shows the equivalent circuit of Fig. 8(a).

In order to maintain the composite capacitance C in the above formula (1) at a predetermined value, the portion where the capacitance Cr of the cavity resonator 33 becomes larger must reduce the ratio of the capacitance Cs of the clamp ring.

As a result, relative to the capacitance part Cr, the ratio of the capacitance part Cs is set to increase, so that the oscillation frequency of the N/2-1 mode cannot be separated from the oscillation frequency of the π mode, that is, the so-called problem of unstable operation caused by the mode jump occurs. It is difficult to achieve both high efficiency of movement and stability at the same time.

In order to secure a large distance between the plate-shaped blades 13, it is conceivable to reduce the thickness of each blade, but if the thickness is reduced, the magnetron cannot withstand the heat capacity.

Contents of the invention

Therefore, the object of the present invention is related to solving the above-mentioned problems, and the present invention provides a magnetron that can reduce the capacitance portion of the clamping ring even when the distance between the plate-shaped blades for realizing high efficiency is narrowed. The ratio of Cs to the capacitive part Cr of the cavity resonator divided by the adjacent plate blades is set to be large, and the oscillation frequency of the N/2-1 mode can be separated from the oscillation frequency of the π mode. Therefore, even under operating conditions Even if there is a slight change, it is possible to prevent the mode jump caused by the proximity of the N/2-1 mode and the π mode, and achieve high efficiency and operational stability.

The above object can be achieved with the following structure.

(1) The magnetron includes: a roughly cylindrical anode cylinder, an even number of plate-shaped plates fixed on the inner peripheral surface of the anode cylinder radially from the inner peripheral surface of the anode cylinder to the central axis; Blades, an anode frame equipped with large and small clamping rings that alternately electrically connect these plate-shaped blades, and a cathode frame mounted on the central axis of the anode frame, the front ends of each plate-shaped blade located on the central axis side of the anode cylinder are connected from the A range of a predetermined length L from the front end is formed in a stepped shape in which the thickness of the plate is reduced.

(2) In the above (1), when the thickness of the base end side of the plate-shaped blade is t ₀ , the thickness of the front end portion of the stepped thinned wall is t ₁ , and the mutual front end portions of the adjacent plate-shaped blades are When the spacing distance between them is W and the number of plate blades is N, N, L, t ₀ , and t ₁ are respectively set to satisfy the following formula.

W/(t ₁ +W)≤0.5

L≥{(t ₀ -t ₁ )/2}÷tan(180/N)

In the magnetron described in (1) above, even if the distance between the plate-shaped blades is narrowed for high efficiency, the front ends of the adjacent plate-shaped blades are stepped and become the surfaces facing each other. The structure in which the gap is gradually opened can suppress an increase in the opposing area in the narrow gap between the tip portions of the plate-shaped blades, compared with the tip of the prior art in which the tip and the tapered surface are made.

Therefore, it is possible to suppress the reduction of the capacitance portion Cr of the cavity resonator, which is affected by the opposing area of the tip portions of the adjacent plate-shaped blades and the distance between the opposing surfaces. As a result, since the ratio of the capacitive portion Cs of the clamp ring portion to the capacitive portion Cr of the cavity resonator partitioned by the adjacent plate-shaped blades can be set to be large, the oscillation frequency of the N/2-1 mode can be changed from The oscillation frequency of the π mode is pulled apart, which can increase the separation degree from the unstable adjacent mode.

Therefore, even when the operating conditions change slightly, the mode jump caused by the proximity of the N/2-1 mode and the π mode can be prevented, and since the most stable and high-efficiency π mode oscillation can be continued, high efficiency can be achieved at the same time and motion stability.

For the magnetron described in (1) above, by setting N, L, t ₀ , t ₁ , the oscillation efficiency can be maintained above 70%, which can prevent excessive thinning of the front end of the plate blade and prevent The durability of the tip portion of the blade against heat decreases.

Description of drawings

Fig. 1 (a) is the longitudinal sectional view of the anode frame of an embodiment of the magnetron of the present invention, and Fig. 1 (b) is the plane view of the anode frame shown in Fig. 1 (a);

Fig. 2 is an enlarged view of mutual front ends of adjacent plate-shaped blades shown in Fig. 1;

Fig. 3 is a comparison diagram of the microwave oscillation characteristics produced by the magnetron of one embodiment shown in Fig. 1 and the microwave oscillation characteristics of the magnetron using existing plate blades;

Fig. 4 is an enlarged view showing another embodiment of the front end portions of adjacent plate-shaped blades of the magnetron of the present invention;

Fig. 5 is a longitudinal sectional view showing a general structure of a conventional magnetron;

Fig. 6 is the perspective view of the main part of the anode frame of the magnetron shown in Fig. 5;

Fig. 7 (a) is the longitudinal sectional view of the anode frame of the magnetron shown in Fig. 5, and Fig. 7 (b) is the plane view of Fig. 7 (a);

FIG. 8( a ) is an enlarged view illustrating a conventional measure for securing a distance between adjacent plate-shaped vane tip portions, and FIG. 8( b ) is a diagram showing its equivalent circuit.

Detailed ways

The best embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 shows an embodiment of the anode framework that magnetron of the present invention uses, and Fig. 1 (a) is the longitudinal sectional view of anode framework, and Fig. 1 (b) is the plane view of the anode framework shown in Fig. 1 (a) .

The magnetron of this embodiment is a microwave oscillating tube operating at a fundamental frequency of 5800MHz. Structures other than the anode frame 51 such as a magnet, a frame-shaped yoke, and a filter circuit are the same as those of the prior art shown in FIG.

The anode frame 51 of the present embodiment has the following structure, which includes a substantially cylindrical anode body 53 on which a cathode frame is mounted on the central axis; The inner circumference of 53 is fixedly mounted on the anode cylinder 53 radially towards the central axis; large and small clamping rings 56a, 56b, 57a, 57b make these plate blades 54 alternately electrically connected; antenna 59, which is used for Any plate blade 54 of microwave output is connected.

In the case of the present embodiment, the number of plate-shaped blades 54 is 18, and the periphery of the action space 61 between the front end surface of each plate-shaped blade 54 and the cathode frame is divided into 18 by the above-mentioned 18 plate-shaped blades 54. A cavity resonator 63.

On the other hand, in the case of the anode frame 51 of this embodiment, the front end of each plate blade 54 located on the central axis of the anode cylinder 53 is made from the front end to a predetermined length (depth) L as shown in FIG. 2 . Thin stepped Df with a plate thickness of only Δt.

Assuming that the plate thickness of the base end side of the plate-shaped vane 54 is t ₀ , and the plate thickness of the front end where both surfaces are thinner by Δt in a stepped shape Df is t ₁ , the distance between the adjacent plate-shaped vanes 54 between the front ends is t 1 . When the interval distance between is W and the number of plate blades 54 is N, N, L, t ₀ , and t ₁ are respectively set so as to satisfy the following equations (3) and (4).

W/(t ₁ +W)≤0.5 ...(3)

L≥{(t ₀ -t ₁ )/2}÷tan(180/N) ...(4)

In the above-described magnetron of the present embodiment, even if the distance between the plate-shaped blades 54 is narrowed due to high-efficiency, high-magnetization, increase in the number of anode divisions, and reduction of the anode and cathode diameters, the adjacent plate-shaped blades will 54 mutual front ends are due to the stepped Df equipped on both sides to form a structure in which the interval (spacing distance) between the two faces of the plate-shaped blade 54 is slowly opened. In contrast, at the front end portions of the plate-shaped vanes 54 , the increase in the facing area can be suppressed with a narrow interval.

Therefore, the capacitive portion Cr of the hollow resonator 63 which is affected by the opposing area of the tip portions of the adjacent plate-shaped blades 54 and the distance between the opposing surfaces can be suppressed and reduced. As a result, the ratio of the capacitive portion Cs of the clamping ring portion composed of the clamping rings 56a, 56b, 57a, 57b is set as Increasing , can make the oscillation frequency of the N/2-1 mode far away from the oscillation frequency of the π mode, realize mode separation, and increase the degree of separation from unstable adjacent modes.

Therefore, even when the operating conditions fluctuate slightly, the most stable high-efficiency π-mode oscillation can be continued by preventing the mode jump due to the proximity of the N/2-1 mode and the π-mode, so that high efficiency can also be achieved at the same time. and movement stability.

In the above formula (4), setting the length L of the thinned front end of the plate-shaped vane 54 within the above-mentioned range means that it is exposed, and it can be seen from the cathode frame that the length L is short and becomes the base end side of the plate-shaped vane 54. Therefore, the step shape Df that separates the distance between the blades due to the concentration of electrons at this corner may not be ignored actually.

By setting N, L, t ₀ , and t ₁ satisfying the above two formulas (3) and (4), the oscillation efficiency can be maintained at, for example, 70% or more, and it is also possible to prevent the front end of the plate blade 54 from being too thin, preventing The durability of the tip portion of the blade against heat decreases.

Fig. 3 is in order to confirm the action effect of this embodiment, the microwave oscillation frequency characteristic in the magnetron of the above-mentioned embodiment measured and replaces the above-mentioned plate-shaped blade 54 with the plate-shaped blade 13 shown in Fig. 8. Microwave oscillation frequency characteristics in a magnetron.

In FIG. 3, the characteristic curve fz is the curve of the conventional magnetron, and the characteristic curve Pz is the curve of the magnetron of this embodiment.

In the characteristic curve fz of the magnetron of the prior art, the oscillation frequency f1 of the π mode is relatively near 5800 MHz, the oscillation frequency f2 of the N/2-1 mode is near 6470 MHz, and the N/2-1 mode is close to the π mode.

In contrast, in the magnetron characteristic curve Pz of the present embodiment, the oscillation frequency P1 of the π mode is relatively near 5800 MHz, the oscillation frequency P2 of the N/2-1 mode is near 6750 MHz, and the N/2-1 mode is away from π mode, mode separation was improved.

In addition, it was confirmed that the peak level in the N/2-1 mode is also greatly reduced in the present embodiment, and it is difficult to cause oscillations other than the π mode.

In the present embodiment, as shown in FIG. 2 , a step shape Df is provided on both surfaces of the tip portion of each plate-shaped vane 54 . However, as shown in FIG. 4, even if the step shape Df is provided on only one surface of the front end of the plate-shaped blade 54, the distance d between adjacent plate-shaped blades and the approaching and reducing the opposing area can be achieved.

Claims (2)

1. A magnetron, comprising: a roughly cylindrical anode cylinder, an even number of plates fixed radially from the inner peripheral surface of the anode cylinder to the central axis and mounted on the inner peripheral surface of the anode cylinder shaped blades, an anode frame equipped with large and small clamping rings that alternately electrically connect these plate-shaped blades, and a cathode frame mounted on the central axis of the anode frame, it is characterized in that each plate-shaped blade located on the central axis side of the anode cylinder The front end portion of the front end is made into a stepped shape with a predetermined length L from the front end to reduce the thickness of the plate. 2. The magnetron according to claim 1, wherein the thickness of the base end side of the plate-shaped blade is t ₀ , the thickness of the stepped thinned front end is t ₁ , and the adjacent plate-shaped When the distance between the front ends of the blades is W and the number of plate-shaped blades is N, N, L, t ₀ , and t ₁ are respectively set to satisfy the following formula W/(t ₁ +W)≤0.5 L≥{(t ₀ -t ₁ )/2}÷tan(180/N).

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